The present invention relates to an X-ray imaging apparatus suitable for use in medical diagnosis.
When medical radiography is carried out using the conventional X-ray imaging apparatus, the resolution and contrast of the reproduced image are likely to be degraded because of scattered X-rays generated from the object to be imaged. A demand for a high-speed X-ray imaging apparatus which enables a short exposure time has arisen these days. The amount of irradiated X-rays must be increased to achieve a high speed operation. However, there is a limitation on increasing the amount of X-rays, because an X-ray generator has a limited load.
Accordingly, Japanese Patent Disclosure (KOKAI) No. 53/7190, for example, discloses an X-ray imaging apparatus including an X-ray generator of the electronic beam scanning type which serves to move the X-ray irradiating position of an X-ray generating target, which has a slit plate positioned between the X-ray generator and the object to be imaged, which has substantially a single slit through which X-rays are allowed to pass, and which has an X-ray image detector positioned behind the slit plate to reproduce the X-ray image which is formed after X-rays pass through the slits and the object. In the case of this type of X-ray imaging apparatus, however, it is difficult to obtain a sufficient amount of X-rays and thus high S/N (signal to noise ratio) because the X-ray generator is of the stationary target type. It is also difficult to achieve high resolution because the X-ray detecting characteristic is discontinuous.
U.S. Pat. No. 4,179,100 discloses an apparatus wherein an X-ray image is reproduced in such a way that an X-ray beam which has passed through a single slit of a slit plate is further passed through an object to be imaged, and then is introduced into an X-ray detector such as a fluorescent screen or an X-ray image intensifier to be converted to an optical image. However, the object, slit plate, X-ray generator and the like are mechanically moved. In this case, it is necessary to move them over a wide range of length in order to image the whole area of the object. Thus, it is difficult to achieve a high speed operation or a short exposure time. In addition, blur is still left in the reproduced X-ray image because of scattered X-rays generated in the object and because of veiling glares generated in the image intensifier by the scattered rays and the discharging of undesired floating electrons, thereby making it difficult to achieve a satisfactory resolution and contrast.